The present invention generally relates to a golf ball including a layer containing relatively long reinforced fibers and methods for forming such golf ball, where the fibers may be arranged randomly or non-randomly. The present invention is also directed to a golf ball including a layer reinforced with relatively long fibers to increase its stiffness and its impact resistance.
Conventional golf balls have primarily two functional components: the core and the cover. The primary purpose of the core is to be the xe2x80x9cspringxe2x80x9d of the ball or the principal source of resiliency. The core may be solid or wound. The primary purpose of the cover is to protect the core. Multi-layer solid balls include multi-layer core constructions or multi-layer cover constructions, and combinations thereof. In a golf ball with a multi-layer core, the principal source of resiliency is the multi-layer core. In a golf ball with a multi-layer cover, the principal source of resiliency is the single-layer core.
Two-layer solid balls are made with a single-solid core, typically a cross-link polybutadiene or other rubber, encased by a hard cover material. Increasing the cross-link density of the core material can increase the resiliency of the core. As the resiliency increases, however, the compression may also increase making the ball stiffer, thereby reducing driver spin rates. In an effort to make golf balls with improved performance characteristics, manufacturers have used thermoplastics in various layers in multi-layer golf balls. Some thermoplastic materials have a low flexural modulus, such that layers formed therefrom produce golf balls with driver spin rates at higher than desirable levels. Such high spin rates, although allowing a more skilled player to maximize control of the golf ball, can also cause golf balls to have severely parabolic trajectories and do not achieve sufficient distance. Thus, manufacturers often try to strike a balance between spin rate and distance. By adding fillers in thermoplastic layers, the flexural modulus or stiffness of such layers increases, so that the golf balls produced have lower spin rates and can achieve greater distances. As flexural modulus increases in these golf balls, however, impact resistance decreases. Consequently, such golf balls may lack sufficient impact resistance to withstand repeated club impacts. This lack of impact resistance has made filled thermoplastics impractical for use in golf balls.
Therefore, a need exists for a golf ball with a filled thermoplastic layer that exhibits an acceptably high flexural modulus (for lower driver spin) in combination with sufficiently high impact resistance.
Accordingly, the present invention is directed to a golf ball with a core and a polymeric layer reinforced with relatively long fibers.
The present invention is also directed to a golf ball with a layer comprising relatively long fibers embedded in a thermoplastic matrix to increase the flexural modulus and the impact resistance of the thermoplastic matrix. This layer can be the cover, a portion of the cover, an intermediate layer, a portion of the intermediate layer, or any layer in the golf ball.
The present invention is also directed to a golf ball with a fiber-reinforced layer where the fibers may be arranged in random or non-random pattern in the layer.
The present invention is directed to a golf ball comprising a core and at least one layer encasing the core, wherein at least a portion of the encasing layer is made from a pultruded polymer and wherein said protruded polymer comprises a plurality of discrete fibers orientated in a predetermined pattern and embedded in a polymeric matrix. In one embodiment, said portion of the encasing layer is made by compression molding shells formed by injection molding the pultruded polymer, and the orientation of the fibers in said portion of the encasing layer is different than the predetermined pattern. The encasing layer may be a sandwich layer comprising an inner layer, an outer layer and an intermediate layer, wherein the intermediate layer is made from a pultruded polymer. The fibers are at least about 1 mm long, preferably about 1 mm to about 5 mm long, more preferably about 1 mm to about 3 mm long, and most preferably about 1.5 mm long. The predetermined pattern of the fibers in the pultruded polymer comprises the fibers arranged substantially parallel to each other.
In another embodiment, the reinforced portion of the encasing layer is made by compression molding shells cut from a sheet of the pultruded polymer, wherein the orientation of the fibers in said portion of the encasing layer is substantially the same as the predetermined pattern of the fibers in the pultruded polymer. The fibers are at least about 1 mm long, and can be as long as about one-half of the circumference of the encasing layer.
The encasing layer can be a cover layer or an intermediate layer, and the fibers can be aramid fibers, glass fibers, carbon fibers, metallic fibers, ceramic fibers, cotton fibers, flax, jute, hemp, silk, among others. The polymeric matrix of the pultruded polymer is preferably a thermoplastic polymer. In accordance to one aspect of the invention, suitable thermoplastic polymer has a flexural modulus between about 500 psi to about 30,000 psi, and in accordance to another aspect of the invention suitable thermoplastic polymer has a flexural modulus greater than about 70,000 psi or greater than about 80,000 psi.
The present invention is also directed to a golf ball comprising a core and at least one layer encasing the core, wherein the encasing layer is reinforced by a plurality of discrete fibers arranged in a predetermined pattern embedded in a polymeric matrix. The predetermined pattern comprises discrete fibers arranged substantially parallel to each other. The encasing layer is preferably made from a pultruded polymer. The fibers are at least about 1 mm long and can be as long as one-half of the circumference of the encasing layer.